I recently bought a house with an unfinished basement. The former owner had started finishing it, but didn't get far. He did put 2x4 framing up along the outside poured concrete walls, but only left about half an inch of space between the studs and the concrete. I guess his plan was to insulate with fiberglass batt insulation.
I would like to avoid ripping out the framing, but do not want to insulate with fiberglass. What is my best option? Can I do rigid foam board between the studs and push thinner strips of foam in the half-inch space between the studs and concrete?